(1) Field of the Invention
The invention relates to a structure to dissipate heat generated by an electrical device, and more particularly to a structure dissipating the heat generated by the electrical device by a dissipating opening provided on a PC board located under the electrical device.
(2) Description of the Prior Art
In application of electrical wares, the heat-dissipation is always a crucial and essential problem. Especially for the electrical devices, a good heat dissipating mechanism usually guarantees a stable performance of an electrical device. On the contrary, an electrical device operated under an ill-dissipating condition will inevitably lead to an unstable performance and reduce its operation life.
A fan mechanism for generating forced airflow and dissipating fins for diffusing heat are usually seen in conventional heat dissipating system. In the fan mechanism, airflow is generated by the fan to rapidly take away the heat generated by any electrical devices in the nearby area. On the other hand, the fin structure 3 as typically shown in FIG. 1 is usually mounted on the top surface of a target electrical device 2 of a PC board 1 to diffuse the heat generated by the electrical device 2.
However, for some types of electrical devices, the top surface is designed for a specific purpose and cannot be used as a base for mounting a fin structure. Those electrical devices include CCD, CMOS IC, some sensing IC, or the like. For example, as shown in FIG. 2, in an electrical device 2a such as a CCD (Charge Coupled Device), a viewing window 21 for an optical purpose is provided on the top surface of the electrical device 2a mounted on a PC board 1. Apparently, for such a type of electrical devices 2a, the dissipating fin structure 3 as shown in FIG. 1 can not be used. However, another solution for heat dissipating is still necessary.
As shown in FIG. 2, the top surface of the electrical device 2a is not suitable for establishing a fin structure. Therefore, an upper dissipating plate 4 made of conductive material and mounted between the electrical device 2a and the PC board 1 is generally utilized to diffuse the generated heat. Of course, respective lead slots 41 are needed on the dissipating plate 4 for allowing the leads 23 of the electrical device 2a to pass through.
From the aforesaid description, it is obvious that the conventional heat dissipating structure, such as the fin structure, is not applicable to the electrical device whose top surface can not be provided as a mounting base. Though the upper dissipating plate 4 can enhance the heat dissipation efficiency to some extent, the accommodation space on a PC board 1 is generally limited for installing an large dissipating plate 4 that is capable of great heat diffusion. Besides, the heat dissipated from the edge of the upper dissipating plate 4 will inevitably affect other adjacent electrical devices. Moreover, since the dissipating plate 4 is sandwiched by the electrical device 2a and the PC board 1, the heat dissipating performance of the dissipating plate 4 can not be good.